Cap Layer For Bit Line Resistance Reduction

ABSTRACT

Memory devices and methods of forming memory devices are described. The memory devices comprise a substrate with at least one film stack. The film stack comprises a polysilicon layer on the substrate; a bit line metal layer on the polysilicon layer; a cap layer on the bit line metal layer; and a hardmask on the cap layer. The memory device of some embodiments includes an optional barrier metal layer on the polysilicon layer and the bit line metal layer is on the barrier metal layer. Methods of forming electronic devices are described where one or more patterns are transferred through the films of the film stack to provide the bit line of a memory device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of and claims priority to U.S.application Ser. No. 16/164,236, filed Oct. 18, 2018, the entiredisclosure of which is hereby incorporated by reference herein.

TECHNICAL FIELD

Embodiments of the present disclosure pertain to the field of electronicdevices and electronic device manufacturing. More particularly,embodiments of the disclosure provide electronic devices including a bitline with reduced resistance and methods of forming same.

BACKGROUND

The electrically-conductive interconnect layers of modern integratedcircuits are generally of very fine pitch and high density. A single,small defect in the precursor metal film which ultimately forms ametallic interconnect layer of an integrated circuit can be sopositioned as to seriously damage the operational integrity of theintegrated circuit.

Bit line stack deposition suffers from a number of potential issues.Surface reaction of the metal and silicon nitride hardmask can occur dueto high deposition temperatures experienced in the formation of thehardmask. The bit line resistance can increase due to inter-diffusion ofsilicon into the bit line and metal atoms into the silicon nitridehardmask. Additionally, grain growth metals can be difficult to use dueto metal surface roughness caused by high temperature silicon nitridehardmask formation.

Therefore, there is a need in the art for bit line stacks and/or methodsof forming bit lines with lower resistivity.

SUMMARY

One or more embodiments of the disclosure are directed to memory devicescomprising a substrate having at least one film stack thereon. The filmstack comprises a polysilicon layer on the substrate, a bit line metallayer on the polysilicon layer, a cap layer on the bit line metal layerand a hardmask on the cap layer.

Additional embodiments of the disclosure are directed to methods offorming a memory device. A substrate having a conductive layer with abarrier layer thereon and a bit line metal layer on the barrier layer isprovided. A cap layer is formed on the bit line metal layer at atemperature less than or equal to about 500° C. A hardmask is formed onthe cap layer at a temperature greater than or equal to about 650° C.Elements of the hardmask are substantially prevented from migrating intothe bit line metal layer.

Further embodiments of the disclosure are directed to methods of forminga memory device. A substrate with a film stack thereon is provided. Thefilm stack comprises a polysilicon layer, a barrier metal layer on thepolysilicon layer, a barrier layer on the barrier metal layer, a bitline metal layer on the barrier layer, a cap layer on the bit line metallayer, a hardmask on the cap layer, a carbon hardmask on the hardmask,an anti-reflective coating (ARC) on the carbon hardmask and a patternedspacer layer on the ARC. The ARC, carbon hardmask and hardmask areetched to expose the cap layer. The cap layer, bit line metal layer,barrier layer, barrier metal layer and polysilicon layer are etched toform a substrate with a plurality of dynamic random access memory (DRAM)film stacks.

BRIEF DESCRIPTION OF THE DRAWING

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments. The embodiments as described herein areillustrated by way of example and not limitation in the figures of theaccompanying drawings in which like references indicate similarelements.

FIG. 1 illustrates a circuit diagram of a dynamic memory cell in a DRAMmemory having improved properties in accordance with one or moreembodiments of the present disclosure;

FIG. 2 illustrates a schematic representation of a film stack accordingto one or more embodiments;

FIG. 3 illustrates a flowchart method for forming a film stack accordingto one or more embodiments;

FIG. 4 illustrates a flowchart method for forming an electronic deviceaccording to one or more embodiments; and

FIGS. 5A through 5J show a schematic representation of a process forforming an electronic device in accordance with one or more embodimentsof the disclosure.

DETAILED DESCRIPTION

Before describing several exemplary embodiments of the disclosure, it isto be understood that the disclosure is not limited to the details ofconstruction or process steps set forth in the following description.The disclosure is capable of other embodiments and of being practiced orbeing carried out in various ways.

Bit line stacks and methods for forming bit line stacks with reducedresistance are provided. One or more embodiments of the disclosureadvantageously address the issue of resistivity reduction in spite ofthe need for shrinking nodes. In some embodiments, the resistivity ofthe bit line is reduced by providing cleaner interfaces with existingbit line metals and by changing the bit line metal. Some embodiments ofthe disclosure advantageously provide one or more of flexibility inchoice of the bit line metal; flexibility of temperature for siliconnitride hardmask deposition; ensure clean metal-dielectric interfacesresulting in lower resistivity; or minimizes or eliminates risk ofcontamination of high temperature silicon nitride hardmask depositionchamber by new bit line metals.

Some embodiments of the disclosure provide low temperature depositionmethods using a cap layer to prevent roughening of the bit line metalsurface when metal of choice exhibits grain growth characteristics. Insome embodiments, high density non-porous films are used to act as gooddiffusion barriers at elevated temperatures. Some embodiments providedielectric materials, such as silicon nitride (SiN) or siliconcarbonitride (SiCN), to act as a cap film to minimize or eliminateadverse impact on the RC time constant by acting as a good diffusionsbarrier for bit line metal and SiN hardmask. The RC time constant is thetime associated with charging a capacitor through a resistor to apercentage of full charge or to discharge the capacitor to a fraction ofthe initial voltage. The RC time constant is equal to the product of thecircuit resistance and the circuit capacitance. Some embodiments of thedisclosure advantageously provide deposition processes at lowtemperatures (e.g., <500° C.). Some embodiments provide compatibledeposition processes with underlying bit line metals to minimize oreliminate surface reactions during film deposition.

One or more embodiments of the disclosure generally provide structureswhich include one or more low-resistivity features formed from a thinfilm refractory metal (e.g., tungsten) as may be implemented in bit linestructures and/or gate stacks. Some embodiments include methods forforming bit line stacks. By way of example, a bit line stack structureformed in accordance with embodiments of the present disclosure may be amemory type semiconductor device, such as a DRAM type integratedcircuit.

FIG. 1 illustrates a schematic circuit diagram of a one transistor onecapacitor cell 100 such as may be used in DRAM memories. The memory celldepicted in FIG. 1 comprises a storage capacitor 110 and a selectiontransistor 120. The selection transistor 120 is formed as a field effecttransistor and has a first source/drain electrode 121 and a secondsource/drain electrode 123 between which an active region 122 isarranged. Above the active region 122 are the gate insulating layer ordielectric layer 124, typically a thermally grown oxide, and gateelectrode/metal 125 (called word line in memory devices), together whichact like a plate capacitor and can influence the charge density in theactive region 122 in order to form or block a current conducting channelbetween the first source/drain electrode 121 and the second source/drainelectrode 123.

The second source/drain electrode 123 of the selection transistor 120 isconnected to a first electrode 111 of the storage capacitor 110 via ametal line 114. A second electrode 112 of the storage capacitor 110 isin turn connected to a capacitor plate which may be common to storagecapacitors of the DRAM memory cell arrangement. The second electrode 112of storage capacitor 110 can be connected to electrical ground via metalline 115. The first source/drain electrode 121 of the selectiontransistor 120 is furthermore connected to a bit line 116 in order thatthe information stored in storage capacitor 110 in the form of chargescan be written in and read out. The write in or read out operation iscontrolled via a word line 117 or gate electrode 125 of the selectiontransistor 120 and bit line 116 which is connected to the firstsource/drain electrode 121. The write in or read out operation occurs byapplying a voltage to produce a current conducting channel in the activeregion 122 between the first source/drain electrode 121 and the secondsource/drain electrode 123.

FIG. 2 illustrates a portion of a memory device 200 in accordance withone or more embodiment of the disclosure. FIG. 3 illustrates anexemplary processing method 300 for forming the memory device 200illustrated in FIG. 2. The skilled artisan will recognize that the filmstacks illustrated in the drawings is an exemplary portion (the bit lineportion) of a memory device.

Referring to FIGS. 2 and 3, formation of the memory device 200comprises, at operation 310, providing a substrate 210 upon which a filmstack 205 can be formed. As used in this specification and the appendedclaims, the term “provided” means that the substrate is made availablefor processing (e.g., positioned in a processing chamber).

As used in this specification and the appended claims, the term“substrate” refers to a surface, or portion of a surface, upon which aprocess acts. It will also be understood by those skilled in the artthat reference to a substrate can refer to only a portion of thesubstrate, unless the context clearly indicates otherwise. Additionally,reference to depositing on a substrate can mean both a bare substrateand a substrate with one or more films or features deposited or formedthereon.

A “substrate” as used herein, refers to any substrate or materialsurface formed on a substrate upon which film processing is performedduring a fabrication process. For example, a substrate surface on whichprocessing can be performed include materials such as silicon, siliconoxide, strained silicon, silicon on insulator (SOI), carbon dopedsilicon oxides, amorphous silicon, doped silicon, germanium, galliumarsenide, glass, sapphire, and any other materials such as metals, metalnitrides, metal alloys, and other conductive materials, depending on theapplication. Substrates include, without limitation, semiconductorwafers. Substrates may be exposed to a pretreatment process to polish,etch, reduce, oxidize, hydroxylate, anneal and/or bake the substratesurface. In addition to film processing directly on the surface of thesubstrate itself, in the present disclosure, any of the film processingsteps disclosed may also be performed on an under-layer formed on thesubstrate as disclosed in more detail below, and the term “substratesurface” is intended to include such under-layer as the contextindicates. Thus for example, where a film/layer or partial film/layerhas been deposited onto a substrate surface, the exposed surface of thenewly deposited film/layer becomes the substrate surface.

In some embodiments, the substrate 210 provided comprises a film stack205 comprising a polysilicon layer 215 and a bit line metal layer 240.In some embodiments, the substrate 210 provided comprises a polysiliconlayer 215 and the bit line metal layer 240 is formed as part of method300.

In some embodiments, the substrate 210 comprises an oxide layer (notshown) on a silicon wafer. In some embodiments, the oxide layer is anative oxide formed on the silicon wafer. In some embodiments, the oxidelayer is intentionally formed on the silicon wafer and has a thicknessgreater than the thickness of a native oxide film. The oxide layer canbe formed by any suitable technique known to the skilled artisanincluding, but not limited to, thermal oxidation, plasma oxidation andexposure to atmospheric conditions.

In some embodiments, the substrate 210 provided in operation 310 furthercomprises a barrier metal layer 220 (also referred to as a conductivelayer) on the polysilicon layer 215. The barrier metal layer 220 can beany suitable conductive material. In some embodiments, the barrier metallayer 220 comprises one or more of titanium (Ti), tantalum (Ta),titanium silicide (TiSi) or tantalum silicide (TaSi). In someembodiments, the barrier metal layer 220 comprises titanium. In someembodiments, the barrier metal layer 220 consists essentially oftitanium. In some embodiments, the barrier metal layer 220 comprises orconsists essentially of tantalum. In some embodiments, the barrier metallayer 220 comprises or consists essentially of titanium silicide. Insome embodiments, the barrier metal layer 220 comprises or consistsessentially of tantalum silicide. As used in this manner, the term“consists essentially of” means that the subject film comprises greaterthan or equal to about 95%, 98%, 99% or 99.9% of the stated element orcomposition, on an atomic basis. For example, a barrier metal layer 220consisting essentially of titanium has a film that is greater than orequal to about 95%, 98%, 99% or 99.5% titanium as deposited.

In some embodiments, the substrate 210 provided in operation 310 furthercomprises a barrier layer 230 on the conductive layer (barrier metallayer 220). The barrier layer 230 can be formed between the barriermetal layer 220 and the bit line metal layer 240. In some embodiments,the method 300 includes an operation before operation 310 where the bitline metal layer 240 is formed on the barrier layer 230. The barrierlayer 230 can be any suitable barrier layer material. In someembodiments, the barrier layer 230 comprises one or more of a nitride oran oxide of the barrier metal layer 220. In some embodiments, thebarrier layer 230 consists essentially of a nitride of the barrier metallayer 220. For example, a barrier layer 230 consisting essentially oftitanium nitride means that the sum of the titanium and nitrogen atomsin the film make up greater than or equal to about 95%, 98%, 99% or99.5% of the barrier layer 230 on an atomic basis as deposited.

In some embodiments, the barrier metal layer 220 comprises titanium (Ti)and the barrier layer 230 comprises titanium nitride (TiN). In someembodiments, the barrier metal layer 220 consists essentially oftitanium and the barrier layer 230 consists essentially of titaniumnitride. In one or more embodiments, the barrier metal layer 220comprises a metal selected from one or more of cobalt (Co), copper (Cu),nickel (Ni), ruthenium (Ru), manganese (Mn), silver (Ag), gold (Au),platinum (Pt), iron (Fe), molybdenum (Mo), rhodium (Rh), titanium (Ti),tantalum (Ta), silicon (Si), or tungsten (W). In one or more specificembodiments, the barrier metal layer 220 (conductive material) comprisesone or more of titanium (Ti), copper (Cu), cobalt (Co), tungsten (W), orruthenium (Ru). In some embodiments, the barrier layer 230 comprises anitride, oxynitride, carbonitride, or oxycarbonitride of the metal inbarrier metal layer 220. In some embodiments, the barrier metal layer220 comprises (or consists essentially of) tantalum or tantalum silicideand the barrier layer 230 comprises (or consists essentially of)tantalum nitride. In some embodiments, the barrier metal layer 220comprises (or consists essentially of) titanium or titanium silicide andthe barrier layer 230 comprises (or consists essentially of) titaniumnitride.

In some embodiments, the bit line metal layer 240 is included in thesubstrate provided in operation 310 of method 300. The bit line metallayer 240 can be deposited by any suitable technique known to theskilled artisan. In some embodiments, the bit line metal layer 240comprises one or more of tungsten (W), ruthenium (Ru), iridium (Ir),platinum (Pt), rhodium (Rh) or molybdenum (Mo). In some specificembodiments, the bit line metal layer 240 comprises or consistsessentially of one or more of ruthenium or tungsten.

The thickness of the bit line metal layer 240 can be varied. In someembodiments, the bit line metal layer 240 has a thickness in a range ofabout 100 Å to about 300 Å, or in the range of about 120 Å to about 250Å, or in the range of about 140 Å to about 200 Å, or in the range ofabout 160 Å to about 180 Å.

The bit line metal layer 240 can be deposited by any suitable techniqueknown to the skilled artisan. In some embodiments, the bit line metallayer 240 is deposited by one or more of chemical vapor deposition,atomic layer deposition or physical vapor deposition.

At operation 320, a cap layer 250 is formed on the bit line metal layer240. The cap layer 250 of some embodiments is deposited at a lowertemperature than would typically be used for formation of a subsequenthardmask 260 layer. Without being bound by any particular theory ofoperation, it is believed that the lower deposition temperatureminimizes diffusion of the cap layer 250 elements into the bit linemetal layer 240. In some embodiments, it is believed that the lowtemperature deposition of the cap layer 250 minimizes grain growth atthe bit line metal layer 240 interface and minimizes the effect of grainsize and roughness on the resistivity of the resulting bit line metallayer 240.

The cap layer 250 can be deposited by any suitable technique known tothe skilled artisan. In some embodiments, the cap layer 250 is depositedby one or more of chemical vapor deposition or atomic layer deposition.

The cap layer 250 of some embodiments comprises the same compound as asubsequent hardmask 260. In some embodiments, the cap layer 250comprises one or more of silicon nitride, silicon carbonitride orsilicon carbide. In some embodiments, the cap layer 250 consistsessentially of silicon nitride. In some embodiments, the cap layer 250consists essentially of silicon carbonitride. In some embodiments, thecap layer 250 consists essentially of silicon carbide.

The thickness of the cap layer 250 can be varied to minimize the impactof high temperature formation of a hardmask 260. In some embodiments,the cap layer 250 has a thickness in the range of about 30 Å to about 50Å.

The deposition temperature of the cap layer 250 can be controlled to,for example, preserve the thermal budget of the device being formed. Insome embodiments, the cap layer 250 is formed at a temperature less thanor equal to about 500° C., or about 450° C., or about 400° C., or about350° C., or about 300° C. In some embodiments, the cap layer 250 isformed at a temperature in the range of about 350° C. to about 550° C.,or in the range of about 400° C. to about 500° C.

At operation 330, a hardmask 260 is formed on the cap layer 250. Thehardmask 260 of some embodiments is formed in a furnace at a temperaturegreater than about 600° C., about 650° C., about 700° C. or about 750°C.

In some embodiments, the hardmask 260 comprises the same composition asthe cap layer 250. In some embodiments, the cap layer 250 and thehardmask 260 comprise or consist essentially of silicon nitride, siliconoxide, silicon carbide, or silicon carbonitride. In some embodiments,the hardmask 260 has a different density than the cap layer 250. In someembodiments, the hardmask 260 has a different porosity than the caplayer 250. In some embodiments, the hardmask 260 has a differentdeposition temperature than the cap layer 250.

In some embodiments, the bit line metal layer 240 comprises or consistsessentially of tungsten and one or more of the cap layer 250 or hardmask260 comprises or consists essentially of silicon nitride. In someembodiments, the bit line metal layer 240 comprises or consistsessentially of ruthenium and one or more of the cap layer 250 orhardmask 260 comprises or consists essentially of silicon oxide orsilicon nitride.

In some embodiments, the elements of the hardmask 260 are substantiallyprevented from migrating into the bit line metal layer 240. For example,if the hardmask 260 comprises silicon and nitrogen atoms, silicon ornitrogen atoms are substantially prevented from migrating into the bitline metal layer 240. As used in this manner, the term “substantiallyprevented” means that less than or equal to about 10% or 5% of thehardmask 260 elements migrate into the bit line metal layer 260 throughthe cap layer 250.

Additional embodiments of the disclosure are directed to methods offorming a memory device. The skilled artisan will recognize that themethods described can form a portion of a memory device (e.g., a bitline) which can be part of a complete memory device. FIG. 4 illustratesa process flow for an exemplary method 400 for forming a memory device.FIGS. 5A through 5J show schematic representations of the various layersand films during formation of the electronic device 500 (see FIG. 5J)following a method 400 in accordance with FIG. 4. The skilled artisanwill recognize that the method 400 can start with various configurationsof the substrate and films/layers thereon. For example, the method 400could start with the configuration illustrated in any of FIGS. 5Bthrough 51, concluding at the electronic device 500 illustrated in FIG.5J. The films/layers described can be the same as the films/layersdescribed with respect to FIG. 2, and the reference numerals used todescribe the films/layers are consistent with those of the embodiment ofFIG. 2.

At operation 410, a substrate 210 is provided for processing. Thesubstrate 210 has a film stack 204 formed thereon, as shown in FIG. 5A.The film stack 204 comprises the film stack 205 illustrated in FIG. 2with additional layers/films formed thereon, as shown in FIG. 5A. Insome embodiments, the film stack 204 comprises a polysilicon layer 215on the substrate 210, or directly on the substrate 210. As used in thismanner, the term “directly on” means that the subject films are formedwithout intervening layers or films. The skilled artisan will recognizethat any of the films/layers described as being “on” another film/layercan be “directly on” or can have intervening layers.

An optional barrier metal layer 220 is on the polysilicon layer 215, ordirectly on the polysilicon layer 215. In some embodiments, there is nobarrier metal layer 220 in the film stack 204. An optional barrier layer230 can be on the optional barrier metal layer 220, directly on theoptional barrier metal layer 220 or directly on the polysilicon layer215. A bit line metal layer 240 is on the optional barrier layer 230 ordirectly on the optional barrier layer 230, or directly on the barriermetal layer 220, or directly on the polysilicon layer 215. A cap layer250 is on the bit line metal layer 240 or directly on the bit line metallayer 240. A hard mask 260 is on the cap layer 250 or directly on thecap layer 250.

The film stack 204 of some embodiments further comprises one or more ofa carbon hardmask 270, anti-reflective coating (ARC) 280 or spacer layer290. In some embodiments, the carbon hardmask 270 is formed on ordirectly on the hardmask 260. The carbon hardmask 270 can be anysuitable carbon containing material that can be used as a hardmask fordevice patterning. In some embodiments, the carbon hardmask 270comprises a high-density carbon film.

In some embodiments, the carbon hardmask 270 comprises a diamond-likecarbon material. For diamond-like carbon materials, the bulk propertiessought may include, without limitation, high density and modulus (e.g.,higher sp3 content, more diamond-like) and low stress (e.g., <−500 MPa).Some embodiments of diamond-like carbon films have one or more of highdensity (e.g., >1.8 g/cc), high modulus (e.g., >150 GPa) and/or lowstress (e.g., <−500 MPa). In some embodiments, the carbon hardmask 270has low stress and high sp3 carbon content.

The carbon hardmask 270 can be formed by any suitable process known tothe skilled artisan. The carbon hardmask 270 can be formed at anysuitable temperature depending on, for example, the thermal budget ofthe device being formed, the process used for formation and/or thereactive species used for formation of the film.

In some embodiments, an anti-reflective coating (ARC) 280 is formed onor directly on the carbon hardmask 270. In some embodiments, the ARC 280is formed directly on the hardmask 260 without an intervening carbonhardmask 270. The anti-reflective coating 280 of some embodimentscomprises one or more of a silicon ARC (SiARC), a bottom ARC (BARC) ordielectric ARC (DARC). In some embodiments, the ARC 280 and carbonhardmask 270 are reversed so that the ARC 280 is directly on thehardmask 260 and the carbon hardmask 270 is directly on the ARC 280.

The ARC 280 can be formed by any suitable process known to the skilledartisan. In some embodiments, the ARC 280 is deposited using one ofdeposition techniques, such as but not limited to a chemical vapordeposition (“CVD”), a physical vapor deposition (“PVD”), molecular beamepitaxy (“MBE”), metalorganic chemical vapor deposition (“MOCVD”),atomic layer deposition (“ALD”), spin-on, or other insulating depositiontechniques known to one of ordinary skill in the art of microelectronicdevice manufacturing.

A patterned spacer layer 290 is on or directly on the ARC 280. In someembodiments, the patterned spacer layer 290 is directly on the carbonhardmask 270 with or without an ARC 280 below the carbon hardmask 270.The pattern of the patterned spacer layer 290 can be formed by anysuitable patterning technique known the skilled artisan including, butnot limited to, lithography. The patterned spacer layer 290 has apattern that exposes portions of the top surface 282 of the ARC 280, orthe top surface 272 of the carbon hardmask 270.

At operation 420, the film stack 204 is etched to expose the cap layer250, as shown in FIG. 5D. Operation 420 can include any number ofprocesses sufficient to etch the ARC 280, the carbon hardmask 270 andthe hardmask 260 to expose the cap layer 250. The skilled artisan willrecognize that the process of FIG. 4 is merely representative of onepossible process and series of operations.

In the illustrated embodiment, at operation 422, the pattern of thepatterned spacer layer 290 is transferred to the ARC 280 to form apatterned ARC 281, as shown in FIG. 5B. The pattern can be transferredto the ARC 280 by any suitable technique known to the skilled artisanincluding, but not limited to, isotropic etch. The pattern of thepatterned ARC 281 is essentially the same as the pattern of thepatterned spacer layer 290 and exposes the top surface 272 of the carbonhardmask 270. As used in this manner, the term “essentially the same”means that the transferred pattern is aligned with the source patternand allows for slight imperfections to be transferred, as will beunderstood by the skilled artisan. Reference to the patterns being the“same” as the previous pattern also recognizes that small variations andimperfections are expected and within the scope of the disclosure. Insome embodiments, the ARC 280 is etched through patterned spacer layer290 to form the patterned ARC 281.

As shown in FIG. 5B, the patterned spacer layer 290 is reduced in height(thickness) to form reduced patterned spacer layer 291. The reduction inthickness of the patterned spacer layer can occur at the same time asthe pattern transfer, or in a separate process. In some embodiments, thepatterned spacer layer 290 is etched at the same time as the ARC 280 toform the reduced patterned spacer layer 291 and patterned ARC 281. Insome embodiments, the patterned spacer layer 290 is completely removedduring the pattern transfer process.

In operation 424, as shown in FIG. 5C, the pattern of the patterned ARC281 is transferred into the carbon hardmask 270 to form a patternedcarbon hardmask 271. The pattern of the patterned carbon hardmask 271 isessentially the same as the pattern of the pattern ARC 281 and exposes atop surface 262 of the hardmask 260. The pattern can be transferred tothe carbon hardmask 270 by any suitable technique known to the skilledartisan including, but not limited to, isotropic etch, selective etch oranisotropic etch.

In the illustrated process, the reduced patterned spacer layer 291 isremoved with the pattern transfer into the carbon hardmask 270. Theremoval of the reduced patterned spacer layer 291 can occur in the sameprocess or different process than the pattern transfer.

In operation 426, as shown in FIG. 5D, the pattern of the patternedcarbon hardmask 271 is transferred into the hardmask 260 to form apatterned hardmask 261 and expose the top surface 252 of the cap layer250. The pattern can be transferred from the patterned carbon hardmask271 to the patterned hardmask 261 by any suitable technique known to theskilled artisan including, but not limited to, isotropic etch, selectiveetch or anisotropic etch.

In the embodiment illustrated in FIG. 5D, the thickness of the patternedcarbon hardmask 271 is reduced to form a reduced patterned carbonhardmask 273. In some embodiments, reducing the thickness of thepatterned carbon hardmask 271 occurs at the same time as transferringthe pattern to the hardmask 270. In some embodiments, reducing thethickness of the patterned carbon hardmask 271 occurs in a separateprocess than the pattern transfer.

At operation 430, which is optional, the width W₁ of the individualmandrels 265 of the patterned hardmask 261 is reduced to a smaller widthW₂. The trimmed mandrels 266, as shown in FIG. 5E, have a smaller widthW₂ than the width W₁ of the reduced patterned carbon hardmask 272.Trimming the width of the mandrels 265 can be done by any suitabletrimming process known to the skilled artisan including, but not limitedto, plasma exposure.

At operation 435, as shown in FIG. 5F, the reduced patterned carbonhardmask 272 is removed from the trimmed patterned hardmask 263 or fromthe patterned hardmask 261 (if the trimming operation 430 is omitted).Removal of the reduced patterned carbon hardmask 272 can be done by anysuitable process known to the skilled artisan including, but not limitedto, selective etching.

At operation 440, a substrate 210 with a plurality of DRAM film stacks205 are formed, as shown in FIG. 5J. To arrive at the substrate 210 withthe plurality of DRAM film stacks 205, the cap layer 250, bit line metallayer 240, barrier layer 230, barrier metal layer 220 and polysiliconlayer 215 are etched.

At operation 442, as shown in FIG. 5G, the pattern of trimmed patternedhardmask 263 is transferred to the cap layer 250 and bit line metallayer 240 to form a patterned cap layer 251 and patterned bit line metallayer 241, respectively, and expose the top surface 232 of the barrierlayer 230. If the mandrel 265 in FIG. 5D is not trimmed, then thepattern of the patterned hardmask 261 is transferred to the cap layer250 and bit line metal layer 240. The difference in processes being thewidth of the pattern mandrels.

The illustrated embodiment shows the pattern transfer to the cap layer250 and bit line metal layer 240 at the same time. The method 400 showsthe pattern transfers split into operations 442 and 444. In someembodiments, as in operation 442, the pattern is transferred to the caplayer 250 to form a patterned cap layer 251 and expose a top surface(not shown) of the bit line metal layer 240. The pattern of thepatterned cap layer 251 can then be transferred, as in operation 444, tothe bit line metal layer 240 to form the patterned bit line metal layer241.

In the embodiment illustrated in FIG. 5G, the thickness of the patternedhardmask 263 is reduced to form a reduced patterned hardmask 267. Insome embodiments, reducing the thickness of the patterned hardmask 263occurs at the same time as transferring the pattern to the cap layer 250and/or bit line metal layer 240. In some embodiments, reducing thethickness of the patterned hardmask 263 occurs in a separate processthan the pattern transfer to either the cap layer 250 or bit line metallayer 240.

At operation 446, the pattern of the patterned bit line metal layer 241is transferred to the barrier layer 230 and to barrier metal layer 220to form a patterned barrier layer 231 and patterned metal layer 221. Thepattern transfer can be to both the barrier layer 230 and barrier metallayer 220 at the same time or in separate processes. The flow chartmethod 400 of FIG. 4 shows a single operation 446 to transfer thepattern to both the barrier layer 230 and the barrier metal layer 220.The illustrated schematics show separate processes. In FIG. 5H, thepattern is transferred to the barrier layer 231 to form patternedbarrier layer 231 and expose the top surface 222 of the barrier metallayer 220. In FIG. 5I, the pattern is transferred to the barrier metallayer 220 to form patterned metal layer 221 and expose the top surface217 of the polysilicon layer 215. Transferring the pattern to thebarrier layer 230 and barrier metal layer 220 can be done by anysuitable technique known to the skilled artisan including, but notlimited to, selective etching.

In operation 448, as shown in FIG. 5J, the pattern of the patternedmetal layer 221 is transferred to the polysilicon layer 215 to form apatterned polysilicon layer 216, and expose the top surface 212 of thesubstrate 210. The resultant electronic device 500 has a plurality offilm stacks 205 similar to that illustrated in FIG. 2. In embodimentswhere some of the layers are omitted, the plurality of film stacks willalso omit the same layers. Transferring the pattern into the polysiliconlayer can be done by any suitable technique including, but not limitedto, selective etching.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the materials and methods discussed herein(especially in the context of the following claims) are to be construedto cover both the singular and the plural, unless otherwise indicatedherein or clearly contradicted by context. Recitation of ranges ofvalues herein are merely intended to serve as a shorthand method ofreferring individually to each separate value falling within the range,unless otherwise indicated herein, and each separate value isincorporated into the specification as if it were individually recitedherein. All methods described herein can be performed in any suitableorder unless otherwise indicated herein or otherwise clearlycontradicted by context. The use of any and all examples, or exemplarylanguage (e.g., “such as”) provided herein, is intended merely to betterilluminate the materials and methods and does not pose a limitation onthe scope unless otherwise claimed. No language in the specificationshould be construed as indicating any non-claimed element as essentialto the practice of the disclosed materials and methods.

Reference throughout this specification to “one embodiment,” “certainembodiments,” “one or more embodiments” or “an embodiment” means that aparticular feature, structure, material, or characteristic described inconnection with the embodiment is included in at least one embodiment ofthe disclosure. Thus, the appearances of the phrases such as “in one ormore embodiments,” “in certain embodiments,” “in one embodiment” or “inan embodiment” in various places throughout this specification are notnecessarily referring to the same embodiment of the disclosure.Furthermore, the particular features, structures, materials, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

Although the disclosure herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent disclosure. It will be apparent to those skilled in the art thatvarious modifications and variations can be made to the method andapparatus of the present disclosure without departing from the spiritand scope of the disclosure. Thus, it is intended that the presentdisclosure include modifications and variations that are within thescope of the appended claims and their equivalents.

What is claimed is:
 1. A memory device comprising: a substrate having atleast one film stack thereon, the film stack comprising, a polysiliconlayer on the substrate; a bit line metal layer on the polysilicon layer;a cap layer on the bit line metal layer; and a hardmask on the caplayer.
 2. The memory device of claim 1, further comprising a barriermetal layer between the polysilicon layer and the bit line metal layer.3. The memory device of claim 2, further comprising a barrier layerbetween the barrier metal layer and the bit line metal layer.
 4. Thememory device of claim 3, wherein the metal layer comprises one or moreof titanium (Ti), tantalum (Ta), titanium silicide (TiSi) or tantalumsilicide (TaSi) and the barrier layer comprises titanium nitride (TiN).5. The memory device of claim 1, wherein the bit line metal layercomprises one or more of tungsten (W), ruthenium (Ru), iridium (Ir) ormolybdenum (Mo), platinum (Pt) or rhodium (Rh).
 6. The memory device ofclaim 1, wherein the cap layer comprises silicon nitride (SiN), siliconcarbonitride (SiCN), or silicon carbide (SiC).
 7. The memory device ofclaim 6, wherein the cap layer has a thickness in a range of about 30 Åto about 50 Å.
 8. The memory device of claim 7, wherein the bit linemetal layer has a thickness in a range of about 100 Å to about 300 Å. 9.The memory device of claim 1, wherein the hardmask comprises siliconnitride (SiN).
 10. The memory device of claim 9, wherein the cap layercomprises silicon nitride having a different density and/or porosityand/or deposition temperature than the hardmask.
 11. The memory deviceof claim 2, wherein the barrier metal layer comprises one or more ofcobalt (Co), copper (Cu), nickel (Ni), ruthenium (Ru), manganese (Mn),silver (Ag), gold (Au), platinum (Pt), iron (Fe), molybdenum (Mo),rhodium (Rh), titanium (Ti), tantalum (Ta), silicon (Si), or tungsten(W).
 12. The memory device of claim 1, further comprising a carbonhardmask on the hardmask, an anti-reflective coating (ARC) on the carbonhardmask and a patterned spacer layer on the ARC, wherein the ARC, thecarbon hardmask and the hardmask are etched to expose a patterned caplayer by transferring the pattern of the patterned spacer layer into theARC, reducing a thickness of the patterned spacer layer and forming apatterned ARC, transferring the pattern of the patterned ARC into thecarbon hardmask, removing the patterned spacer layer and forming apatterned carbon hardmask, transferring the pattern of the patternedcarbon hardmask into the cap layer, removing the patterned ARC andforming a patterned cap layer, and trimming and removing the carbonhardmask from the patterned cap layer.
 13. The memory device of claim12, wherein the patterned cap layer, bit line metal layer, barrierlayer, barrier metal layer and polysilicon layer are etched to form asubstrate with a plurality of dynamic random access memory (DRAM) filmstacks.
 14. A method of forming a memory device, the method comprising:providing a substrate having a conductive layer with a barrier layerthereon and a bit line metal layer on the barrier layer; forming a caplayer on the bit line metal layer at a temperature less than or equal toabout 500° C.; and forming a hardmask on the cap layer at a temperaturegreater than or equal to about 650° C., wherein elements of the hardmaskare substantially prevented from migrating into the bit line metallayer.
 15. The method of claim 14, wherein the cap layer comprises oneor more of silicon nitride or silicon carbonitride.
 16. The method ofclaim 15, wherein the cap layer has a thickness in a range of about 30 Åto about 50 Å.
 17. The method of claim 16, wherein the cap layer isdeposited by a chemical vapor deposition or atomic layer depositionprocess.
 18. The method of claim 17, wherein the hardmask comprisessilicon nitride.
 19. The method of claim 18, wherein the hardmask isdeposited using a furnace at a temperature greater than or equal toabout 650° C.